A gene that causes a wide range of bacteria to become resistant to antibiotics has been found in the water supply in Delhi, with worrying implications for the rest of the globe.

International travel and medical tourism have already brought the gene, known as NDM-1, to the UK. A team of scientists reported last year that they had found NDM-1 positive bacteria in a small number of patients who had visited India for kidney or bone marrow transplants, dialysis, pregnancy care or burns treatment, while others had undergone cosmetic surgery.

A paper by Timothy Walsh from Cardiff University and colleagues, published in the Lancet Infectious Diseases journal, reveals that the gene, known as NDM-1, is widespread in the water used for cooking, washing and drinking in Delhi. It will inevitably be brought into hospitals in the gut flora of patients. The potential for movement around the world is high.

NDM-1 can cause many types of bacteria – including E coli and Klebsiella pneumoniae – to become resistant to powerful antibiotics called carbapenems, which are used when other antibiotics fail to work. The team also found the gene had spread to bacteria that cause cholera and dysentery. "Worryingly, dysentery caused by this particular isolate is currently untreatable," said Mark Toleman, one of the authors.

The findings are published on World Health Day, which this year is dedicated to preserving the healing powers of the antibiotics we still have. The World Health Organisation warns that more than 25,000 people die every year in the EU alone from infections caused by antibiotic-resistant bacteria.

"We need to raise the alert that we are at a critical point where antibiotic resistance is reaching unprecedented levels and new antibiotics are not going to arrive quickly enough," said Zsuzsanna Jakab, WHO regional director for Europe.

She said antibiotics were being taken for granted and overused. "There are now superbugs that do not respond to any drug. Given the growth of travel and trade in Europe and across the world, people should be aware that until all countries tackle this, no country alone can be safe."

There are few new antibiotics in the pharmaceutical pipeline, because they have proved hard to discover and are not lucrative investments for drug companies – new drugs would be kept as a last resort and used very infrequently to begin with.

The scientists involved in the study in New Delhi took samples both from tap water and seepage water collected in pools in streets or in rivulets. The NDM-1 gene was found in two of 50 drinking water samples and 51 of 171 seepage samples.

Poor sanitation in India, where 650 million people do not have access to a flush toilet and probably not to clean water either, is a major issue in the spread of bacteria carrying the gene. High temperatures, which are important for NDM-1 mobility, a crowded population, massive antibiotic over-use, under-use and misuse and poor infection control also contribute.

The situation is made worse by the government's refusal to accept the problem, said Toleman. "Following the publication of this study, the Indian government took draconian measures against the Indian scientists who collaborated with us and our colleagues were threatened," said Toleman.

"This had the effect of severing these productive collaborations and the Indian authorities were in denial of the massive problems southern Asia is facing."

But he added that he thought India was "starting to come out of denial". It has now taken steps towards introducing a surveillance programme. "That's a massive step in the right direction," he said.